An Introduction to the Muscular System

An Introduction to the Muscular System
Consists only of skeletal muscles Muscle Organization and Function Muscle organization affects power, range, and speed of muscle movement Fascicles Muscle cells (fibers) are organized in bundles (fascicles)

Fascicle Arrangement Classification of Skeletal Muscles
By the way fascicles are organized By relationships of fascicles to tendons Organization of Skeletal Muscle Fibers Four patterns of fascicle organization 1. Parallel 2. Convergent 3. Pennate 4. Circular

Fascicle Arrangement Parallel Muscles
Fibers parallel to the long axis of muscle, e.g., ___________________ 1 in.2 (6.45 cm2) of cross section develops 50 lb (23 kg) of tension

Fascicle Arrangement Convergent Muscles
A broad area converges on attachment site (tendon, aponeurosis, or raphe) Muscle fibers pull in different directions, depending on stimulation, e.g., _______________________

Fascicle Arrangement Pennate Muscles Form an angle with the tendon
Do not move as far as parallel muscles Contain more myofibrils than parallel muscles Develop more tenson than parallel muscles Unipennate Fibers on one side of tendon, e.g., ________________ Bipennate Fibers on both sides of tendon, e.g., _________________ Multipennate Tendon branches within muscle, e.g., __________________ Unipennate Fibers on one side of tendon For example, extensor digitorum Bipennate Fibers on both sides of tendon For example, rectus femoris Multipennate Tendon branches within muscle For example, deltoid

Fascicle Arrangement Circular Muscles Also called sphincters
Open and close to guard entrances of the body, e.g., _________muscle of the mouth

Muscle Attachments to Other Tissues
Origins and Insertions Muscles have one fixed point of attachment (______) and one moving point of attachment (______________) Most muscles originate or insert on the skeleton _________ is usually __________ to insertion The origin is usually the proximal end of the muscle. The insertion is usually the distal end. Also, the action of each muscle will usually aid in muscle identification.

Actions Movements produced by muscle contraction Body movements For example, flexion, extension, adduction, etc. Described in terms of bone, joint, or region

Muscle Opposition Agonists and antagonists work in pairs: When one contracts, the other stretches Such as flexors–extensors, abductors–adductors, etc.

Naming Skeletal Muscles
Descriptive Names for Skeletal Muscles Location in the body Origin and insertion Fascicle organization Relative position Structural characteristics Action

Location in the Body Identifies body regions For example, temporalis muscle Origin and Insertion First part of name indicates origin Second part of name indicates insertion For example, genioglossus muscle Lingual muscles with origin in the chin or mandible and insertion near the tongue. Actions depress and protrude the tongue.

Fascicle Organization Describes fascicle orientation within muscle i.e., rectus (straight), transversus, oblique

Relative Position Externus (superficialis) Visible at body surface Internus (profundus) Deep muscles Extrinsic Muscles outside an organ Intrinsic Muscles inside an organ

Structural Characteristics Number of tendons bi = 2, tri = 3 Shape Trapezius, deltoid, rhomboid Size Many terms refer to muscle size

Descriptive Terms for Muscle Size Longus = long Longissimus = longest Teres = long and round Brevis = short Magnus = large Major = larger Maximus = largest Minor = small Minimus = smallest

Action Movements For example, flexor, extensor, retractor

Muscular System Overview
Divisions of the Muscular System Axial muscles Position head and spinal column Move rib cage 60% of skeletal muscles Appendicular muscles Support pectoral and pelvic girdles Support limbs 40% of skeletal muscles

Axial Musculature The Axial Muscles
Divisions based on location and function Muscles of head and neck Muscles of vertebral column Oblique and rectus muscles Muscles of pelvic floor There are about 146 named skeletal muscles in the body (depending upon how you name and count them) and it is way beyond the scope of my interest or this course to learn them all. It is appropriate, however, to name the largest and most important of them and to convey a sense of how they operate.

Axial Musculature Six Muscle Groups of the Head and Neck
Muscles of facial expression: Originate on skull Extrinsic eye muscles: Originate on surface of orbit (Control position of eye) Muscles of mastication: Move the mandible Muscles of the tongue: Names end in glossus Muscles of the pharynx: Begin swallowing process Anterior muscles of the neck: Control position of larynx Depress the mandible Support tongue and pharynx

Axial Musculature Muscles of Facial Expression
Orbicularis oris: constricts the mouth opening ________________: moves food around the cheeks Muscles of the epicranium (scalp) Temporoparietalis – Tenses the scalp Occipitofrontalis – Raises eyebrows, wrinkles forehead Platysma (Covers anterior surface of neck) – Tenses skin of neck, depresses mandible

Axial Musculature Figure 11–4a Muscles of Facial Expression.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Figure 11–4b Muscles of Facial Expression.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Six Extrinsic Eye Muscles (Extra ocular): Action
Inferior rectus: Eye looks down Medial rectus: Eye looks medially Superior rectus: Eye looks up Lateral rectus: Eye looks laterally ______________: Eye rolls, looks up and laterally Superior oblique: Eye rolls, looks down and laterally

Axial Musculature Figure 11–5a,b Extrinsic Eye Muscles.
Inferior rectus: Eye looks down Medial rectus: Eye looks medially Superior rectus: Eye looks up Lateral rectus: Eye looks laterally Inferior oblique: Eye rolls, looks up and laterally Superior oblique: Eye rolls, looks down and laterally Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Figure 11–5c, d Extrinsic Eye Muscles.
Inferior rectus: Eye looks down Medial rectus: Eye looks medially Superior rectus: Eye looks up Lateral rectus: Eye looks laterally Inferior oblique: Eye rolls, looks up and laterally Superior oblique: Eye rolls, looks down and laterally Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Figure 11–6a Muscles of Mastication.
When we talk about the muscles of the skull… There are 2 large muscles on each side of the skull that close the jaw. One of them, the temporalis, can be felt to contract at the temples when you clench your jaw. The other, called the masseter, arises from the cheekbone (zygomatic bone) and can be felt by putting your finger below and in front of your ear when you clench your jaw. This is the strongest jaw muscle. Muscles that open the mouth are located beneath the chin, and additional muscles that adjust the position of the jawbone are located medially to it. A complicated network of 11 muscles that surround the eyes and mouth can adjust facial features. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Figure 11–9a Muscles of the Anterior Neck.
Put the palm of your hand on your forehead and try to knod your head and at the same time touch the medial portion of your clavicle you can feel long tendons that go up from the front of the neck toward the back of the skull. These two prominent tendons can be felt arising from the top of the sternum and proceeding toward the back of the jaw. These belong to the sternocleidomastoid muscles, which flex the neck when you are nodding “yes.” Push on your forehead with the flat of your palm and you will feel these muscles contract. Together they flex the neck. Alone, one side bend the head toward the shoulder and turns the face to the opposite side. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature [INSERT FIG. 11.10a]
Figure 11–10a Muscles of the Vertebral Column. The relatively superficial muscle of the back of the neck is called the splenius; this muscle helps to bend the neck backwards or rotate the head, and covers over deeper neck muscles that also adjust the position of the skull. Proceeding downwards from the splenius is a large collection of back muscles called the erector spinae, which acts to arch the back and move it as a coordinated whole; some portions of the erector spinae extend all the way down to the pelvis. Sometimes these muscles can spasm and their complexity makes spasms difficult to treat. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Axial Musculature Oblique and Rectus Muscles Lie within the body wall
Oblique muscles Compress underlying structures Rotate vertebral column Rectus muscles Flex vertebral column Oppose erector spinae Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Appendicular Musculature
Position and stabilize pectoral and pelvic girdles Move upper and lower limbs Divisions of Appendicular Muscles Muscles of the shoulders and upper limbs Muscles of the pelvis and lower limbs

Muscles of the Shoulders and Upper Limbs Position the pectoral girdle Move the arm Move the forearm and hand Move the hand and fingers The muscles of the upper extremities serve to both anchor the arm onto the body and to move the arm. The first muscles we need to describe are the ones that hold the scapula in place.

Muscles That Position the Pectoral Girdle __________________ Superficial Covers back and neck to base of skull Inserts on clavicles and scapular spines Actions: (1) elavate, retract, depress, or rotate scapula upward; (2) elevate clavicle; (3) extend neck The most superficial muscle that does this is called the trapezius, a triangle-shaped muscle that begins at the base of the neck, fans out to cover the spine of the scapula, and then attaches to all of the thoracic vertebrae. This muscle helps us move our shoulders and, when twisted abnormally during sleep, can give us the sensation of a “crick” in our neck.

Muscles That Position the Pectoral Girdle _________________ and levator scapulae Deep to trapezius Attach to cervical and thoracic vertebrae Insert on scapular border Action of the Rhomboid: Adducts scapula and performs ____________________ motion Action of the ____________ scapulae: ___________ scapula The scapula is also anchored to the vertebral column on the most medial border by two muscles called the rhomboid muscles and the levator scapulae.

[INSERT FIG a] Figure 11–14a Muscles That Position the Pectoral Girdle. The most superficial muscle that does this is called the trapezius, a triangle-shaped muscle that begins at the base of the neck, fans out to cover the spine of the scapula, and then attaches to all of the thoracic vertebrae. This muscle helps us move our shoulders and, when twisted abnormally during sleep, can give us the sensation of a “crick” in our neck. The scapula is also anchored to the vertebral column on the most medial border by two muscles called the rhomboid muscles. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Other Muscles That Position the Pectoral Girdle Serratus anterior: Protracts shoulder, rotates scapula On the chest Originates along ribs Inserts on anterior scapular margin Subclavius: Depresses and protracts shoulder Originates on ribs Inserts on clavicle Pectoralis minor: Depresses and protracts shoulder, rotates scapula, elevates ribs Attaches to scapula

[INSERT FIG b] Figure 11–14b Muscles That Position the Pectoral Girdle. Serratus anterior On the chest Originates along ribs Inserts on anterior scapular margin Subclavius Originates on ribs Inserts on clavicle Pectoralis minor Attaches to scapula Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Arm Deltoid The major abductor (also flexion and extension) Supraspinatus Assists deltoid Subscapularis and Teres major Produce medial rotation at shoulder Infraspinatus and Teres minor Produce lateral rotation at shoulder The muscles that move the arm serve both to anchor the arm onto the body and to move the arm. A major superficial muscle that covers the shoulder is the deltoid muscle. The deltoid inserts onto the humerous and helps abduct the arm. If you touch your fingertips to your shoulder, it will contract when you raise your arm. The supraspinatus, infraspinatus, subscapularis, and teres major are muscles of the rotator cuff. They are called the rotator cuff because these muscles and associated tendons surround the head of the humerus and prevent it from being dislocated. They all insert on the humerus and stabilize it.

Figure 11–15a Muscles That Move the Arm. The muscles that move the arm serve both to anchor the arm onto the body and to move the arm. A major superficial muscle that covers the shoulder is the deltoid muscle. The deltoid inserts onto the humerous and helps abduct the arm. If you touch your fingertips to your shoulder, it will contract when you raise or abduct your arm. The supraspinatus, subscapularis, and teres major are 3 of the 4 muscles of the rotator cuff. They are called the rotator cuff because these muscles and associated tendons surround the head of the humerus and prevent it from being dislocated. They all insert on the humerus and stabilize it. Deltoid The major abductor Supraspinatus Assists deltoid Subscapularis and Teres major Produce medial rotation at shoulder Infraspinatus and Teres minor Produce lateral rotation at shoulder Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Figure 11–15b(Part 1 of 2) Muscles That Move the Arm. Supraspinatus Assists deltoid Subscapularis and Teres major Produce medial rotation at shoulder Infraspinatus and Teres minor Produce lateral rotation at shoulder Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Arm Pectoralis major Between anterior chest and greater tubercle of humerus Originates from the sternum and ventral portoins of the ribs Produces ________ at shoulder joint, adduction, and medial rotation at the shoulder Latissimus dorsi Between thoracic vertebrae and humerus Originates from the vertebral column and dorsal ribs Produces ______________ at shoulder joint, adduction, and medial rotation at the shoulder Two large muscles that originate from the chest wall also insert onto the humerus. The ventral chest muscle is called the pectoralis, which originates from the sternum and ventral portions of the ribs. The dorsal muscle is called the latissimus dorsi, which originates from the vertebral column and dorsal ribs. Both are large, strong muscles that pull the humerus closer to the body (adduct it). These muscles are active when an athlete performs a maneuver like the iron cross on the rings.

Figure 11–15 Muscles That Move the Arm. Two large muscles that originate from the chest wall also insert onto the humerus. The ventral chest muscle is called the pectoralis, which originates from the sternum and ventral portions of the ribs. The dorsal muscle is called the latissimus dorsi, which originates from the vertebral column and dorsal ribs. Both are large, strong muscles that pull the humerus closer to the body (adduct it). These muscles are active when an athlete performs a maneuver like the iron cross on the rings. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Forearm and Hand Originate on humerus and insert on forearm Exceptions: The major flexor (biceps brachii) The major extensor (triceps brachii)

Flexors of the Elbow Biceps brachii _____________ elbow Stabilizes shoulder joint Originates on scapula Inserts on _____________ Figure 11–16b Muscles That Move the Forearm and Hand. The biceps brachii form a firm mound on the ventral surface of the arm when we flex the arm. The muscle gets its name from the fact that it originates from 2 places, or “heads”. The 2 heads of the biceps originate from different locations on the scapula and lead to a common tendon that is easily felt at the inner surface of the elbow. The tendon inserts onto the radius and allows us to flex the arm and rotate the radius. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Extensors of the Elbow Triceps brachii ____________ elbow Originates on scapula Inserts on _________ Figure 11–16a Muscles That Move the Forearm and Hand. Located at the back of the arm is the major extensor of the arm, a muscle called the triceps brachii. This muscle has 3 heads rather than 2 and originates from one spot on the scapula (long head) and 2 spots on the humerus itself (medial and lateral heads). Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Flexors of the Wrist Palmaris longus Superficial Flexes wrist Flexor carpi ulnaris Adducts wrist Flexor carpi radialis Abducts wrist The ventral surface of the forearm has 8 muscles that help flex the arm or fingers. Some of the tendons of these muscles are easily felt at the wrist when the hand is held palm up. At the wrist, just below your thumb, you can palpate the strong tendon of a muscle called the flexor carpi radialis if you put your hand, palm upwards, underneath a table and try to flex or bend the hand upwards. Next to this tendon you can feel the pulsations of the radial artery feeding blood to the hand.

Extensors of the Wrist Extensor carpi radialis Superficial Extends wrist Abducts wrist Extensor carpi ulnaris Adducts wrist

Muscles That Move the Forearm and Hand Pronation and supination Pronator teres and supinator Originate on humerus and ulna Rotate radius Pronator quadratus Originates on ulna Assists pronator teres

Figure 11–16b Muscles That Move the Forearm and Hand. Pronator teres and supinator Originate on humerus and ulna Rotate radius Pronator quadratus Originates on ulna Assists pronator teres Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Hand and Fingers Also called extrinsic muscles of the hand Lie entirely within forearm Only ____________ cross wrist (in synovial tendon sheaths) The palm of the hand has 19 muscles that originate on the metacarpal bones and insert via tendons onto the fingers. The fingers do not have muscles. Fingerbones are entirely surrounded by tendons that originate from the palm of the hand or the forearm.

Muscles that Move the Hand and Fingers Tendon sheaths Extensor retinaculum Wide band of connective tissue Posterior surface of wrist Stabilizes tendons of extensor muscles Flexor retinaculum: Anterior surface of wrist Stabilizes tendons of flexor muscles All the muscles that flex the fingers have to pass into the hand underneath a strap of connective tissue called the flexor retinaculum. This covers the “carpal tunnel” that has the carpal bones as a floor. If the flexor muscles of the hand are used repetitively, they may swell and press against the nerves that enter the hand through the carpal tunnel. This results in carpal tunnel syndrome.

Figure 11–16b Muscles That Move the Forearm and Hand. All the muscles that flex the fingers have to pass into the hand underneath a strap of connective tissue called the flexor retinaculum. This covers the “carpal tunnel” that has the carpal bones as a floor. If the flexor muscles of the hand are used repetitively, they may swell and press against the nerves that enter the hand through the carpal tunnel. This results in carpal tunnel syndrome. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Figure 11–18b Intrinsic Muscles of the Hand. All the muscles that flex the fingers have to pass into the hand underneath a strap of connective tissue called the flexor retinaculum. This covers the “carpal tunnel” that has the carpal bones as a floor. If the flexor muscles of the hand are used repetitively, they may swell and press against the nerves that enter the hand through the carpal tunnel. This results in carpal tunnel syndrome. Tendon sheaths Extensor retinaculum Wide band of connective tissue Posterior surface of wrist Stabilizes tendons of extensor muscles Flexor retinaculum: Anterior surface of wrist Stabilizes tendons of flexor muscles Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Figure 11–18a Intrinsic Muscles of the Hand. The palm of the hand has 19 muscles that originate on the metacarpal bones and insert via tendons onto the fingers. The fingers do not have muscles. Fingerbones are entirely surrounded by tendons that originate from the palm of the hand or the forearm. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

On the dorsal side of the forearm, 10 muscles are present that permit straightening or extension of the fingers. Some of them have tendons that are particularly noticeable. If you place your hand on a table palm down and fan your fingers and thumb, a large tendon can be seen occupying the middle of your thumb. This is the tendon of the extensor pollicis longus. It forms one border of a triangular depression in your hand at the base of the thumb called the “anatomical snuff box.” This name comes from the 18th century practice of putting snuff there to sniff into the nose. The other border below is made from the tendon of the flexor pollicis longus. Below that even is the abductor pollicis longus. In the forearm we can also see the extensor digitorum involved in the flexion of fingers, metacarpals, and wrist joints. In the hand, you can see the tendon of the extensor digitorum innervating the fingers. What’s the name of that unlabeled tendon coming in to the proximal and anterior side of the radius? Tendon of the biceps brachii. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

On the anterior side of the forearm we can see the flexor digitorum superficialis: flexion of fingers, metacarpals, and wrist joints. We can also see that the tendon of the biceps brachii is now labeled. As are the muscles for the abductor and extensor pollicus longus. Again we can see the tendon of the extensor digitorum. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles of the Lower Limbs 36 muscles move the bones of the lower extremities: Muscles that move the thigh Muscles that move the leg Muscles that move the foot and toes There are 36 different muscles that move the bones of the lower extremity. We’re going to focus on those that are prominent and necessary for understanding how the leg functions.

Muscles That Move the Thigh Gluteal muscles Lateral rotators Adductors Iliopsoas Ill-e-oh-so-us: muscle spasms here give us low back pain, leg pain, or hip pain or a combination of these.

Muscles That Move the Thigh: Gluteal Muscles Cover lateral surfaces of ilia Gluteus maximus Largest, most posterior gluteal muscle Produces extension and lateral rotation at hip Tensor fasciae latae Works with gluteus maximus Stabilizes iliotibial tract Gluteus medius and gluteus minimus Originate anterior to gluteus maximus Insert on trochanter The arm is abducted away from the body by? We said it’s the major abductor of the arm and you can feel it if you press your fingers into your shoulder while elevating your arm. -Deltoid muscle. The leg is abducted away from the body by an analogous muscle called the gluteus maximus.

Figure 11–19a Muscles That Move the Thigh. a. We can see that the gluteus maximus is very prominent and is the largest and most posterior gluteal muscle. It produces extension and lateral rotation at the hip. b. The gluteus maximus arises from the pelvis and inserts onto the femur. Notice when you’re seated, the ischial tuberosities of the pelvis come in contact with overlying muscle of the gluteus maximus. (Obturator internus = 1 of 6 muscles that laterally rotate the thigh). Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Thigh: Lateral rotators Group of six muscles, including: Piriformis Also hip abduction Obturator (externus and internus) Gemilli (superior and inferior) Quadratus femoris

Muscles That Move the Thigh: Adductors Adductor magnus Produces adduction, extension, and flexion Adductor brevis Hip flexion and adduction Adductor longus Pectineus Gracilis I’m giving you this now because we’ll visit a couple of these in lab.

Muscles That Move the Thigh: Iliopsoas Two hip flexors insert on the same tendon Psoas major Iliacus Ill-e-oh-so-us: muscle spasms here give us low back pain, leg pain, or hip pain or a combination of these. Psoas = so-us Iiiacus = ill-i-ah-cus

Muscles That Move the Leg __________________ of the knee Originate on the ______________________ Originate on the _________________ surface Insert on the patella

Flexors of the Knee ________________________ Biceps femoris Semimembranosus Semitendinosus Sartorius Originates superior to the acetabulum Popliteus Rotates the tibia to unlock the knee Remember that the back (dorsal) surface of the leg is analogous to the front (ventral) surface of the arm. What muscle covers the ventral surface of the arm? Biceps brachii. So it makes sense that a prominent muscle of the back of the thigh is called the biceps femoris. It arises from 2 spots, one on the ischial bone of the pelvis and the other on a long area of the femur. It inserts via a strong tendon onto the fibula. You can feel this tendon at the back of the knee at its lateral margin. At the medial margin of the back of the knee you can feel 2 strong tendons belonging to the semi-tend-in-o-sus and semi-membran-o-sus. All 3 muscles strongly flex the leg at the knee and are termed the hamstring muscles. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Figure 11–20a Muscles That Move the Leg. Biceps femoris flex at the knee and are involved in extension and lateral rotation at the hip. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Leg Extensors of the knee Four muscles of the _______________________ Three vastus muscles Extension at the knee Rectus femoris muscle Flexion at the hip What muscle extends the arm, so moving it away from the axis? Triceps muscle. An analogous muscle in the leg is called the quadriceps femoris. It has 4 heads instead of 3 like the triceps and functions to extend the lower leg.

[INSERT FIG b] Figure 11–20b Muscles That Move the Leg. The quadriceps make up most of the muscle mass that you can feel underneath the skin of the front of the thigh. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Foot and Toes Extrinsic muscles that move the foot and toes include Muscles that produce extension at the ankle Muscles that produce flexion at the ankle Muscles that produce extension at the toes Muscles that produce flexion at the toes

Four Muscles That Produce Extension (plantar flexion) at the Ankle Gastrocnemius - also inversion of the foot, flexion at knee Soleus Fibularis (group) Tibialis posterior The back of the lower leg, or calf, has 6 muscles, but two of them are the most prominent. The most superficial muscle is called the gastroc-nemius. Just beneath it is a flatter muscle called the soleus. Both muscles insert into the heel bone. What’s it called? Calcaneus. They insert onto the calcaneus by a common tendon called the what? Achilles tendon. The Achilles tendon is the largest and strongest tendon in the body. Repair of a ruptured Achilles tendon requires that it be sewn back together and involves a lengthy immobilization of the lower leg.

Figure 11–21a Extrinsic Muscles That Move the Foot and Toes. (Plantaris also involved in extension/plantar flexion at the ankle and flexion at the knee) Calcaneal tendon a.k.a. Achilles tendon Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Move the Foot and Toes The Achilles Tendon The calcaneal tendon (Achilles tendon) Shared by the gastrocnemius and soleus Gastroc-nemius

Muscles That Produce Flexion (Dorsiflexsion) at the Ankle Tibialis anterior Opposes the gastrocnemius (extensor) Except both are involved with inversion of the foot What’s dorsiflexion? Gastroc-nemius Touch the fingertips of both your hands to your shinbone (tibia), just below the knee. Then, flex your foot upwards. What are you doing when you flex your foot? You should feel the contraction of a major muscle called the tibialis anterior. Is it located medial or lateral to the shinbone? Lateral. The tibialis anterior sends a tendon that curves around the medial margin of the big toe and is anchored to the bottom of the foot at the bottom of the 1st metatarsal bone. That’s why it flexes the foot.

Muscles That Produce Extension at the Toes Extensor digitorum longus Extension at joint of toes 2-5 Extensor hallucis longus Extension of joints at great toe Extensor retinacula: fibrous sheaths hold tendons of toes as they cross the ankle The foot has 19 muscles that move the toes. We’ll focus on a few major ones that produce extension and flexion. Many of these other muscles lie beneath the tendons that you can feel on the front of your foot. These tendons are from muscles that originate farther up in the leg.

[INSERT FIG b] Figure 11–21b Extrinsic Muscles That Move the Foot and Toes. Here we can see the tibialis anterior. Another muscle located just lateral to the tibialis anterior is called the fibularis longus. This muscle sends another tendon that curves around the smooth surface of the lateral malleolus of the fibula. This tendon passes beneath the surface of the foot to insert onto the lateral surface of the first metatarsal. Remember the tibialis anterior sends a tendon that curves around the medial margin of the big toe and is anchored at the bottom of the 1st metatarsal bone too. Together, the tendon of the fibularis longus and the tendon of the tibialus anterior form kind of a “stirrup”-shaped structure that supports the bottom of the foot and helps form the arch at the bottom of the foot. Another structure that helps form the arch of the foot is a mass of tough connective tissue on the bottom of the foot called the plantar fascia, which tugs on the lateral and medial margins of the foot. If this tissue becomes inflammed,, a condition known as plantar fasciitis, a long-lasting foot pain, is the result. (Fibularis brevis = eversion of foot and extension/plantar flexion at ankle). Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

[INSERT FIG d] Figure 11–21d Extrinsic Muscles That Move the Foot and Toes. In humans, the right humerous is typically about 5 mm longer than the left humerus. However, there are no significant differences between the average length of the right tibia compared to the left tibia. What accounts for the asymmetry of the arm bones and not the leg bones? What’s the tibialis anterior do? Flexion/dorsiflexion at the ankle. What muscle is it opposing? Gastroc-nemius. Whats the gastroc-nemis do? Extension/ plantar flexian at the ankle. What does the Soleus do? Same thing. Where do the gastroc-nemius and soleus insert? Calcaneus. What’s the name of their common tendon? Achillies tendon or calcaneal tendon. What bone is the medial malleolus on? Tibia. What’s the major abductor of the arm? Deltoid. Of the leg? Gluteus maximus (arises in the pelvis and inserts on the humerus). Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscles That Produce Flexion at the Toes Flexor digitorum longum Flexion at joint of toes 2-5 Flexor hallucis longus Flexion at joints of great toe Oppose the extensors

Figure 11–21c Extrinsic Muscles That Move the Foot and Toes. The flexors are called the flexor digitorum longus and the flexor hallucis longus. These guys flex the toes and oppose the extensors. So by flexing we’re doing what? What are the extensors called again? Extensor digitorum longus and extensor hallucis longus. Fibularis longus (Eversion of foot and extension/plantar flexion at ankle). Flexor digitorum longus (Flexion of joints of toes 2-5). Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Intrinsic Muscles of the Foot Muscles that move the tarsals, metatarsals, and phalanges and originate and insert only on those bones

Figure 11–22a Intrinsic Muscles of the Foot. What’s the tibialis anterior do? Flexion/dorsiflexion at the ankle. Where does its tendon go? Curves around the medial margin of the big toes and attaches at the bottom of the 1st metatarsal. It’s going to make a stirrup-shapped structure to help arch and support the bottom of the foot with a tendon from which muscle? Fibularis longus. (Dorsal interossei – abduction at metarsophalongeal joints of toes) (Tendons of extensor digitorum brevis – extension of metarsophalongeal joints of toes) (Abductor hallucis – abduction at metarsophalongeal joint at great toe) (Tendon of extensor hallucis brevis – extension at the metarsophalongeal joint at great toe) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Effects of Aging on the Muscular System
Skeletal muscle fibers become smaller in diameter Skeletal muscles become less elastic Develop increasing amounts of fibrous tissue (fibrosis) Decreased tolerance for exercise Decreased ability to recover from muscular injuries

Integration with Other Systems
Cardiovascular system Delivers oxygen and fuel Removes carbon dioxide and wastes Respiratory system Responds to oxygen demand of muscles Integumentary system Disperses heat from muscle activity Nervous and endocrine systems Direct responses of all systems

Integration with Other Systems
Figure 11–24 Functional Relationships Between the Muscular System and Other Systems. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

An Introduction to the Muscular System

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